1. Technical Field
The present invention relates to an extrusion press and in particular, to an extrusion press device that molds an aluminum alloy, etc., by extrusion molding via a die and, in more particular, to an electrically driven extrusion press that applies the electrically driven system adopted in an injection molding machine of synthetic resin (or a die cast machine that die-casts an aluminum alloy).
2. Background Art
An extrusion press is used to mold a metal product, such as an aluminum sash, by extrusion molding. In the conventional extrusion press, a billet, which is a material, is loaded within a fixed container, extruded by a stem (or extrusion stem) driven by a ram cylinder, and passed through a die attached to the outlet of the container, and thereby, the billet is molded so as to have a predetermined cross-sectional shape. The billet loaded on such a molding machine is supplied by a billet loader. The billet loader is configured so as to grasp the billets one by one sent from a billet carrier arranged on the lateral side of the molding machine and move the billet to a billet load port of the container and then the billet is sent out by the stem and loaded on the container in a state where the billet and the load port are aligned and molded by being extruded under pressure.
Many of the products molded by extrusion molding by the extrusion press are elongated, such as an aluminum sash, and in the case of an elongated product, the billet is extruded for a long time by the stem, and therefore, the ram cylinder that pushes the stem uses a hydraulic system capable of long strokes under high pressure. However, such a conventional extrusion press device uses hydraulic pressure as power (for example, see Patent Literature 1, Patent Literature 2), and therefore, there are problems with regard to the environment (noise, oil spill, etc.), energy saving (running cost), etc. In order to solve such problems, it is desired to realize an electric drive that is used in an injection molding machine of synthetic resin (or die cast machine that die-casts an aluminum alloy). In the case of an electric drive, in general, it is necessary to convert rotational motion of an electric motor, which is a drive in the first stage, into rectilinear motion or reciprocating rectilinear motion.
However, such a mechanism (ball screw and ball nut etc.) that converts rotational motion into rectilinear motion in place of a conventional hydraulic cylinder device capable of continuously outputting a large output capacity required for the extrusion press, for example, 9,800 kN (1,000 tf), or a large output electric servomotor is not realized. Due to this, the electrically driven system is not applied to the extrusion press.
Further, the extrusion press comprises various kinds of devices that move, such as an extrusion stem slide, shear device, die slide device (shear), die changer, and billet loader, and conventionally, these devices adopt the hydraulic system as the ram system does.
The conventional extrusion press is a machine that produces extruded products by driving a plurality of hydraulic press devices by motors and pumps that consume electric power. Not only during the extrusion process but also during processes other than the extrusion process, for example, processes of, such as discard cutting and removal and insertion of the next billet, the same pump and motor are used as a drive source. The pump and motor and auxiliary pump and motor used for extrusion that utilize hydraulic equipment are always in the idling operation even when not necessary for the operation of the device directly, and therefore, power consumption loss occurs.
Further, when a machine user uses a machine for many years, the user needs to perform maintenance and inspection inevitably in order to maintain and manage the machine and it is considered that the time required for maintenance is by far longer in the case where the drive source is a hydraulic source than in the case where only an electric motor is used. The reason is as follows. When the hydraulic equipment is used for many years, trouble, such as deterioration of the hydraulic oil, wear of valves, and oil spill from pipe connections, relates to many parts, such as pumps, valves, manifolds, and pipes, and therefore, it takes much time to troubleshoot the cause and take measures.
Further, when the hydraulic source is used, the hydraulic oil flows out (leak, discharge, etc.) at the time of maintenance, etc., and therefore, the machine operability and working environment deteriorate and there is a risk of fire because containers and dies are used in a high-temperature environment. It is of course possible to use flame resistant hydraulic oil (water-glycol fluid etc.), however, ordinarily the hydraulic oil is used under high pressure in order to make the machine compact and the flame resistant hydraulic oil (water-glycol fluid etc.) is not suitable for use, and therefore, not normally used.
As described above, as the drawbacks of the conventional hydraulic drive system, there are problems as follows. (1) The hydraulic oil is used as a medium, and therefore, it is difficult to realize accurate speeds and positions as in the case of the mechanical operation. (2) The amount of energy consumption is comparatively large and cooling water is required to prevent the oil temperature from rising, and therefore, the running cost is increased. (3) The number of components the circuit pressure of which is high is large and the noise during the operation is high. (4) Since hydraulic oil is used, there exit problems of maintenance, environment, and cost resulting from leak of the hydraulic oil and problems of environment and cost accompanying the disposal of the hydraulic oil.
The extrusion presses are classified into the conventional system (conventional type: billets are supplied between the end surface of the container and the tip end surface of the stem, including the direct type and the indirect type) (for example, see Patent Literature 1), the short stroke system (including the front loading system (for example, see Patent Literature 2) and the rear loading system which are classified based on the position where billets are supplied), etc. The present invention can be applied to either type. In the front loading type, the container is moved to the stem side and billets are supplied in the gap between the end surface of the container and the die and the rear loading type differs from the front loading type in that the stem is moved in the horizontal or vertical direction and billets are supplied in the gap formed when the stem moves (between the container and the crosshead).